The physical and electrical properties of the 811A and Audio Tube 572B are what distinguish them most from one another.
The 811A is a vacuum tube created especially for use in amateur radio and commercial radio applications for sending and amplification of radio signals. It employs a thoriated tungsten filament and has a maximum anode voltage of 1250 volts and a maximum plate dissipation of 63 watts. The tube has a diameter of 2 inches and a height of roughly 5.5 inches.
Contrarily, the Audio Tube 572B is a vacuum tube made specifically for high-fidelity audio amplification applications. With a plate dissipation of 160 watts and a maximum anode voltage of 2000 volts, it employs a filament-cathode design. The tube has a diameter of 2.5 inches and a height of almost 6 inches.
Electrically speaking, the 572B is typically regarded as having superior linearity, less distortion, and greater power handling capacity than the 811A. Because of this, audiophiles who seek high-fidelity sound quality frequently choose the 572B.
Overall, the primary distinction between the Audio Tube 811A and the 572B is their intended purpose and design features, with the 572B being utilized for high-fidelity audio amplification and the 811A being predominantly employed in radio signal transmission.